1. Field of the Invention
The present invention is generally in the field of semiconductors. More specifically, the present invention is in the field of fabrication of compound semiconductors.
2. Background Art
Semiconductor based devices, circuits, and switches employed in various modern applications are often required to display greater power handling capabilities and tolerate higher applied voltages than ever before. One response to these increased device performance demands has been the development and implementation of III-nitride semiconductor devices, such as high electron mobility transistors (HEMTs). In a typical HEMT, for example, a two-dimensional electron gas (2DEG) is generated at a semiconductor heterojunction. The 2DEG represents a very thin conduction layer of highly mobile and highly concentrated charge carriers free to move readily in the two dimensions of that conduction layer, but constrained from movement in a third dimension perpendicular to the conduction layer.
In practice, the ability of a HEMT, or any III-nitride semiconductor device, to perform reliably in the face of a high applied voltage (e.g. voltage greater than 600 volts), depends in part on the charge retention characteristics of the 2DEG or other type of conduction channel. In particular, where charge carriers are insufficiently constrained from dispersing out of a desired conduction zone, for example by movement into a silicon substrate of the device, device performance may be less than optimal. More seriously, under applied voltages of even a few hundred volts, a HEMT may short through its silicon substrate, resulting in device failure. Unfortunately, conventional approaches to III-nitride semiconductor device fabrication have failed to provide optimal charge carrier constraint within the conduction zone when high voltage is applied.
Thus, there is a need to overcome the drawbacks and deficiencies in the art by providing a III-nitride semiconductor device, such as a HEMT, exhibiting high voltage durability. It would be of additional advantage if the proposed solution were to provide an implementation capable of supporting monolithic vertical integration of III-nitride power semiconductor devices and silicon devices.